How many people pay attention to the temperature change of coffee powder when making espresso?

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As a competent barista, have you ever worried that the water temperature of your espresso machine brewing head will deviate? Well, let me tell you that the temperature of the coffee powder you use may vary even more!

The relationship between the temperature change of coffee powder and the quality of the final extracted espresso is often overlooked, but it does exist, and the industry has begun to pay attention to this issue in recent years.

Does your grinder heat the coffee grounds?

There are many different types of coffee grinders available on the market. However, whether it is a flat or conical burr, a ceramic burr disc or a metal burr disc, they all use burrs instead of blades.

This means that there are two blades in the grinder, and the coarseness of the grind is determined by the size of the gap between the two blades. When we grind coffee beans, at least one of the two blades will rotate, then crush or cut the coffee beans into fine particles.

However, this process inevitably involves friction, and everyone should know that friction generates heat. This heat will be directly transferred to other parts of the grinder and the coffee powder itself. Therefore, unless you use an extremely professional grinder, the instant temperature of the grinder will change with the running time.

What do extremely professional grinders look like? They have cooling systems. Including fans, heat exchangers, radiators, etc., to dissipate the heat generated during the grinding process. However, even these grinders with cooling systems cannot completely avoid the heating of the blade disc, nor can they allow baristas to monitor the temperature of the coffee powder.

Depending on how fast you grind and how long you grind, the grinding temperature of the coffee powder can range from 20°C to 80°C, with a maximum temperature difference of 60°C. Such a large temperature difference is enough to have a huge impact on your Espresso extraction, resulting in fluctuations in quality and stability.

What is the effect of changing the temperature of coffee grounds?

When the temperature in the grinder rises, you will find that the extraction time of espresso will become shorter and the flow rate will become faster. I believe that people who have worked in coffee shops with large production volumes should have experienced that after continuously grinding and extracting many cups of espresso, your espresso flow rate will change. Therefore, if you don’t want the product to be worse, you have to adjust the grinding degree slightly finer to compensate for this effect.

Then, when the peak production period ends and the frequency of use of the grinder decreases, the temperature will slowly drop, and the grinding degree needs to be adjusted again. Or it sounds like there is no problem. Professional baristas know how to adjust the parameters according to the extraction situation at any time, which is good. However, the more baristas adjust the parameters, the greater the risk of extraction errors, unstable products and improper extraction!

More importantly, as the temperature of the grinder increases, the time it takes to grind the coffee powder will also increase. This will cause a chain reaction. The temperature of the grinder will even affect the coffee powder to water ratio. Because most quantitative grinders on the market actually use timers to fix the amount of ground coffee. You can judge how your espresso is extracted by timing and observing the extraction, but you cannot observe the performance of the grinder changing with temperature.

Why does the temperature of the grinder affect the extraction and grinding time of coffee powder? Unfortunately, most of the research still cannot perfectly explain it. Because the microscopic process of coffee powder grinding is too complicated, we can't even ensure that the analysis is correct.

However, no matter what the reason, one thing we can be sure of is that changes in temperature will have an impact on the extraction of coffee.

Keep the grinder cool.

It is not practical to keep the grinder cool, although it is much easier to speed up the cooling of the grinder to prevent the burrs from heating up too quickly. For example, some grinders use aluminum metal to make the shell to speed up the heat dissipation and keep the burrs cool. However, it is much more expensive to cool something down than to heat it up, because cooling requires more energy.

In other words, as a wealthy coffee lover, you can do everything you can to cool down the grinder even at a huge price, but for a coffee shop owner who pursues efficiency and commercialization, it is impossible and not realistic at all.

In fact, do we really need to spend a lot of money to cool the grinder? Ten years ago, it was generally believed that coffee should be drunk while hot, but now it is clear that some people have questioned this view. The times are developing, and the innovation of science and technology will always refresh people's cognition.

The temperature stability of grinding is more important than the temperature of grinding

Or maybe the key to this problem is not whether the temperature of the blade or the coffee powder is high or low, but the temperature change itself.

Irish Barista Champion Colin Harmon and his team once conducted a related experiment: they ground several different coffee beans at different temperatures and compared and analyzed the extracted coffee. The results showed that in this experiment, there was no significant difference in the flavor quality extracted from these different coffee beans.

No matter what the temperature of the grinder blade is or how fast the grinding speed is, as long as the temperature is stable, each coffee bean can be extracted into espresso with the same parameters and flavor performance. This study shows that the biggest problem with the temperature of the grinder is not the high or low temperature, but the unstable temperature.

at last

The extraction temperature of coffee powder is not one of the variables we discuss everyday, but it does affect the quality and stability. For a busy coffee shop, the heating of coffee powder caused by the continuous operation of the grinder can indeed cause a series of problems.

But like other parameters in coffee brewing, stability and consistency are often the key. It doesn’t matter what temperature the coffee powder is ground at, what matters is how to keep this temperature stable.

Article translated from: www.perfectdailygrind.com

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